摘要: |
Seven major factors account for approximately half of all traffic delay, and therefore, a great deal of the uncertainty associated with travel time: (1) traffic incidents, (2) weather, (3) work zones, (4) fluctuations in demand, (5) special events, (6) traffic control devices, and (7) inadequate base capacity. These factors often interact, which increases the challenge of reducing the uncertainty of travel time that drivers experience. The overall goal of the SHRP 2 Reliability program is to reduce non-recurrent congestion through incident reduction, management, response, and mitigation of the contributing root causes. Achieving this goal would significantly improve travel time reliability for many types of person and freight trips on the nation's highways. Travel time reliability refers to how travel time varies over time and the impacts of this variance on highway users. In other words, for repeated travel or vehicles traveling the same route, there is an underlying distribution of travel time for a particular trip between two points within a specific time period. Individual travelers respond differently to the factors and uncertainties associated with the travel time. So do those involved in freight transportation. For important trips, such as a trip to the doctor or a just-in-time freight delivery, drivers will build extra time into the trip to ensure a high probability of arrival within a time window. SHRP 2 needs to develop a database archive that contains the data used in each project of the Reliability Focus area. The data will be needed to allow others to validate the research results. Validation of results is critically important to ensure the research was done according to high professional standards and can be replicated. The data also needs to be available for researchers in the future to refine and build on the research results. Consequently the data archive must be long-lived, in the range of 20 to 50 years. This time frame seems reasonable in light of the longevity of the Long-Term Pavement Performance database archive developed under the first Strategic Highway Research Program. Project data types potentially include alphanumeric data, imagery, video, audio, spatial data and computer code. There is a possibility that another set of data types will consist of derived data. Such data might include coefficients of an estimated model. Metadata will be required for each project to characterize the type of data to be stored in the archive and will need to conform to a SHRP 2 specification, a proprietary schema, an ASTM standard, XML, another form of metadata, or some combination. A contractor familiar with various approaches to specifying metadata will need to recommend one. |